1. Field of the Invention
The present invention concerns an arc switching electromechanical switch of the contactor or circuit-breaker type, and, more particularly, to a switch having a fixed contact and a mobile contact respectively disposed on a fixed conductive part and a mobile conductive part.
2. Description of the Prior Art
If a contactor is connected in series with a short-circuit protection device such as a circuit-breaker, for example, on the circuit supplying power to a load, an overcurrent can occur with the contactor contacts closed or virtually closed. Even if the fault current, then flowing through the contractor, is limited by the protection device, it is nevertheless very much greater than the nominal current that the contactor interrupts under normal circumstances. If the fault current causes electrodynamic opening of the contacts, the arc then generated can be accompanied by localized liquidation of the fixed and mobile contacts at the anode and cathode ends of the arc and, if it lasts more than 1 ms to 2 ms, can cause bonding or welding of the contacts when they close again.
To avoid this problem, special arc contacts have been used alongside the main contacts. Another solution is the provision of means for accelerating migration of the arc towards an arc extinction chamber.
An object of the present invention is a simple way of preventing stagnation of the arc generated between the contacts on normal or electrodynamic openings thereof, encouraging the striking and maintaining of a secondary arc.